1. Field of the Invention
This invention relates generally to a master transmitter and servant receiver system with a normally dormant servant receiver. When the servant unit receives a signal from the master transmitter, it will generate a sound or light or both, making it easier for the operator of the master unit to find a servant unit. The servant units are normally off and require no maintenance. The master signal unit may use Radio Frequency (RF), Infrared (IR), or Ultrasonic (Acoustic) or a combination thereof.
2. Description of Related Art
A variety of tag devices have been proposed to locate lost or misplaced objects. Prior art servant receivers are on or cycle on and off through a sleep mode. This results in a constant current drain on the battery power supply. Here, a particular type of switch technology is used in the servant receiver. The signal created by the master or handheld transmitter activates a switch to turn on the power in this servant receiver. Therefore, until a signal is sent by the master transmitter and received by the servant receiver, the servant receiver is off with no drain in the battery. The current technology for tag devices propose replacing the battery every few months in the servant receiver. In this technology, the servant receiver battery would only be on when required to activate the sound and or light, hence, extending the battery life of the receiver to essentially the shelf life of the battery.
There are a large number of patents that seek to solve the general problem solved by this invention, which is helping the owner of the invention locate a particular item to which a tag unit is attached and which responds to a signal from the master unit. None of these address the particular problem addressed here. Some use coded signals (Bender U.S. Pat. No. 6,147,602). Renney U.S. Pat. No. 5,939,981 proposes using multiple sensors which are sensitive to the proximity of the master unit to cause sensors to issue a louder tone. Sacca et al. U.S. Pat. No. 5,638,050 recognizes that battery drain is a problem and proposes a receiver cycling in a given time frame. The activating signal is timed to be longer than the period of time the servant receiver is off, hence, the servant receiver will always be on for at least a portion of the activation signal duration, hence, will respond. Because the servant receiver is cycled on and off, it preserves battery life. The patent is relevant in that it recognizes there is a battery problem and attempts to solve it but does so in an entirely different way from the current invention. The Sacca patent U.S. Pat. No. 5,686,891 is similar to the above described '050 patent. The Rosenthal patent U.S. Pat. No. 6,366,202 proposes an acoustic signal with a piezoelectric transducer to receive the signal. An ultrasonic signal from a transmitter is receiver by a resonator which amplifies it in intensity relative to the signal sound wave. Avoiding false triggering is done by use of a coded sequence from the transmitter. This includes a tone followed by a quiet period, a second tone followed by a second quiet period, followed by a third tone, quiet period, and a fourth and final tone. The Steffen patent U.S. Pat. No. 6,025,783 is an entirely different area but has technology of interest. This proposes a wireless system to detect whether a switch is open or not. For example, it could be used in cars to determine if doors are open or not. A tag circuit is responsive to the transmission signal and is powered by the transmitted signal.